How to write Select * from table t where t.col1=t.col2 in mongodb?

Question

How to write following SQL query in mongodb ?

Select * from table t where t.col1=t.col2

Use `db.col.find({$expr:{$eq:["$col1", "$col2"]}})` – s7vr Mar 02 '18 at 00:37 — s7vr, Mar 02 '18 at 00:37

score 1 · Answer 1 · answered Mar 01 '18 at 22:41

You should use $redact aggregation operator which:

Restricts the contents of the documents based on information stored in the documents themselves.

For instance:

db.col.save({a: 1, b: 1});
db.col.save({a: 2, b: 1});

db.col.aggregate([
    { $redact: {
        $cond: {
           if: { $eq: [ "$a", "$b" ] },
           then: "$$KEEP",
           else: "$$PRUNE"
         }
       }
     }
])

How to write Select * from table t where t.col1=t.col2 in mongodb?

1 Answers1